Seismic Behavior And Calculation Method Of Steel Fiber Reinforced High Strength Concrete Shear Wall With Concrete Filled Steel Tube Columns

Reinforced concrete(RC)shear wall is a common lateral force resisting element in high-rise building that has been widely used in high-frequent earthquake prone area.The observation from recent earthquake reconnaissance indicated that the main reason why the RC shear wall was seriously damaged and even collapsed was its inadequate ductility and energy dissipation.In particular,with the increasing application of high strength concrete(HSC),the transverse dimension of shear wall can be decreased,but the brittleness of reinforced high strength concrete(RHSC)shear wall increases inevitably.Correspondingly,the seismic behavior of RHSC shear wall needs to be improved to meet the higher requirement.In this study,an innovative shear wall,which is referred to as steel fiber reinforced high strength concrete(SFRHSC)shear wall with concrete filled steel tube(CFST)columns,is introduced,based on the high bearing capacity and large stiffness of CFST column and good ductility and strong energy consumption of SFRHSC shear wall.The calculation methods of the shear performance,flexural performance and restoring force behavior for SFRHSC shear wall with CFST columns were established through the cyclic loading experiment on 22 SFRHSC shear wall with CFST columns specimens.The relevant conclusions in this thesis can provide test data and theory basis for compiling the industrial standard in China,entitiled “Design standard for steel fiber reinforced concrete structures”.The main research contents in this thesis are as follows:(1)Crack development and distribution,failure characteristic and load displacement hysteresis curves were measured through the experiments on 22 shear wall specimens under cyclic loading.The effects of shear span ratio,steel fiber volume fraction,concrete strength,axial compression ratio and loading process on the seismic performance of SFRHSC shear wall with CFST columns were discussed.The results showed that steel fiber could effectively control the crack width,improve the distribution of cracks and seismic performance of RC shear wall.With the increase of steel fiber volume fraction,the maximum crack width of RC shear wall decreased,the load displacement hysteresis curve was plumper,the ductility and energy dissipation capacity were enhanced,the deterioration of stiffness and bearing capacity became more slowly.(2)The effects of steel fiber volume fraction,concrete strength,axial compression ratio and shear span ratio on shear capacity of SFRHSC low-rise shear wall with CFST columns were discussed,and the force bearing mechanism was studied.The results showed that the shear capacity increased with the increase of steel fiber volume fraction,concrete strength and axial compression ratio,and the shear mechanism of SFRHSC web was comprehensive action of diagonal strut and struss system.Based on the experimental research and theoretical analysis,the relative calculation models for shear capacity of SFRHSC web and for shear capacity of SFRHSC low-rise shear wall with CFST columns were proposed based on steel fiber distribution,softened truss model,softened strut and tie model and simplified softened strut and tie model.(3)The characteristics of flexural failure of SFRHSC mid-rise shear wall with CFST columns was studied,and the effects of steel fiber volume fraction,depth of steel fiber reinforced concrete layer,concrete strength and axial compression ratio on the flexural capacity of SFRHSC mid-rise shear wall with CFST columns were discussed.The results showed that the flexural capacity increased obviously with the increase of steel fiber volume fraction,concrete strength,depth of steel fiber reinforced concrete layer and axial compression ratio.Finally,the calculation method of flexural capacity of SFRHSC mid-rise shear wall with CFST columns was established with the comprehensive consideration of the influences of steel pipe and steel fiber.(4)The restoring force behavior of SFRHSC mid-rise shear wall with CFST columns was studied,and the hysteresis rule was analyzed.The calculation formulas of every key point on skeleton curve and the calculation method of restoring force behavior applicable to SFRHSC mid-rise shear wall with CFST columns were set up.